is an external unit identifier. The value of u must not be
an asterisk or a Hollerith constant.

position_list

is a list that must contain one unit specifier
([UNIT=]u) and can also contain one of each of the
other valid specifiers:

[UNIT=] u

is a unit specifier in which u must be an external unit
identifier whose value is not an asterisk. An external unit identifier
refers to an external file that is represented by a scalar integer expression,
whose value is in the range 1 through 2147483647. If the optional
characters UNIT= are omitted, u must be the first item in
position_list.

IOSTAT= ios

is an input/output status specifier that specifies the status of the
input/output operation. ios is a scalar variable of type
INTEGER(4) or default integer. When the ENDFILE
statement finishes executing, ios is defined with:

A zero value if no error condition occurs

A positive value if an error occurs.

ERR= stmt_label

is an error specifier that specifies the statement label of an executable
statement in the same scoping unit to which control is to transfer in the case
of an error. Coding the ERR= specifier suppresses error
messages.